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Abstract On Rose Diseases Essay, Research Paper
title = abstract on Rose diseases
Multi-Purpose Fungicide Daconil 2787? Plant Disease Control
This product is widely used for broad spectrum disease control on lawns,
ornamentals and listed
fruits and vegetables. Controls many foliar diseases such as: rust, black spot, leaf
anthracnose and powdery mildew as listed on the label. Also controls conifer
diseases and lawn
diseases such as brown patch, red thread, rust and dollar spot. Can be mixed with
specified on the label to make a multi-purpose spray.
WHAT IS POWDERY MILDEW?
Powdery Mildew looks like white fuzzy powder that accumulates on leaves and stems
predominantly in spring, and again to a lesser degree in fall. It is actually a fungus that
is spread by
millions of microscopic spores. It imbeds itself into tender new growth and feeds on
the sap of the
plant. By the time the naked eye can see the white ‘powder,’ it has already invaded
the plant tissue
and is feeding and reproducing at a rapid pace. As it spreads itself on the surface, it
the cells of the plant leaf, leaving the leaf rippled and curled.
Mildew spores are everywhere in the garden – in the air, the soil, on debris and on
plant surfaces -
ready to sprout when the environment is just right. Warm days (50?-80?F) and cool
elevated humidity and resultant dew provide ideal conditions. Though humidity
growth, it grows on DRY plant surfaces, unlike blackspot which requires immersion in
about seven hours in order for infection to take place.
Tender new growth needs a chance to ‘harden’ and develop its waxy coating that
of a barrier to fungal growth. Therefore, the rosarian must provide protection for new
on a weekly basis.
CONTROLLING POWDERY MILDEW
Controlling mildew doesn’t have to mean spraying the planet into oblivion. It includes
cultural practices and something as simple as WATER.
GENETICS: While rose hybridizers are chastised for breeding OUT fragrance, what
they are trying
to accomplish is breeding IN disease resistance. For scientific reasons beyond
explanation here, rose
genes don’t contain both features – it’s one or the other. Hence, you can expect either
with little disease resistance, or clean plants with little fragrance. Plants with glossy or
are less susceptible to mildew, as the leaf surface is harder for spores to penetrate.
possess a high degree of disease and pest resistance. Where mildew is a constant
problem, the choice
in plantings can help prevent the need for extensive maintenance.
CULTURAL PRACTICE: Planting bushes with sufficient space between them and
away from walls
and fences will provide good air circulation which reduces the chances for mildew.
The annual pruning event plays a major role in disease prevention. Stripping leaves
from the bush at
pruning time, and cleaning up debris in the garden contribute to a cleaner
spraying will at least wipe out last year’s spores, leaving only this year’s to contend
with. Keeping the
centers of the bush open during the growing season will aid air circulation.
Avoid the use of other plant materials with high mildew susceptibility, such as
tuberous begonias. Apply a thick layer of mulch in early spring to cover spores in the
soil that may
have wintered over. WATER is perhaps the most misconceived element surrounding
mildew. Many gardeners still subscribe to the belief that you should NEVER get rose
On the contrary, a high-pressure spray of water will remove mildew spores that
themselves yet, and prevent them from germinating. Higher incidence of mildew
during periods of
rain is caused by the moisture in the air and soil – increasing the humidity that
promotes mildew -
not by water on the leaves. Similarly, watering early in the day will allow the soil
surface to dry out
a bit before the cool night temperatures arrive, reducing humidity from moist soil.
PREVENTION IS THE ONLY CURE
Once powdery mildew is apparent to the eye, it can’t be eradicated. It simply must be
Prevention is achieved by coating the plant tissue with something that provides a
barrier to prevent
fungus from gaining a foothold and invading the plant tissue. Growth is so rapid in
spring that the
leaves unfolding THIS week won’t be protected by what you sprayed LAST week.
This is the reason
you find application schedules of every 7-10 days on most fungicides, and the reason
follow that schedule.
The choice of what the SOMEthing is that you choose to spray is widening.
Fungicides are the most
widely used because they are chemically formulated to specifically combat fungus
reports of non- toxic, environmentally-friendly products such as baking soda and
are proving very encouraging also.
FUNGICIDES are any of a number of chemicals labeled to combat powdery mildew,
and do so by
interfering with its metabolic life process, rendering it unable to grow and spread.
must be in place on the plant before the spores arrive, they do have systemic action -
move into the plant tissue – providing a residual effect for a short period.
Fungicides are available in many forms – liquids (mix readily with water), emulsifiable
(a thicker, usually milky substance), wettable powders (require thorough mixing prior
application). Each has its own properties, all are effective. Most, however, have a
degree of toxicity to humans. Extreme caution should be used to cover eyes, skin and
hair, and use a
painter’s mask or respirator during application. They are mixed at various rates,
tablespoon per gallon of water, and require application every 7-10 days.
BAKING SODA: “New research shows that simple baking soda is a powerful weapon
fungus-caused rose diseases”, wrote Kristi Clark in her September 1992 American
In a world that is becoming increasingly aware of environmental concerns, more
attention is being
paid to finding alternative measures to widespread chemical use. Sodium
(grocery-variety baking soda) was tested originally to determine its effectiveness in
blackspot. During the experiments, it was noticed that no powdery mildew was found
on any of the
Controlled experiments were conducted for some three years, using sodium
potassium bicarbonate in various combinations with insecticidal soap, Sunspray?
oil, or only water. The result: both diseases were subdued by a weekly spraying of
either sodium or
potassium bicarbonate at 3 teaspoons per gallon of water, combined with Sunspray at
per gallon of water. The bicarbonates eliminated the fungi, but addition of the
Sunspray provided a
spreader-sticker action that increased its performance.
Sunspray is available commercially as Safer? Sunspray. As Clark cautioned, do not
concentrations of the solutions, as leaf burn may result. Rain or overhead watering
may wash the
solution off, reducing its effect.
ANTI-TRANSPIRANTS are another group of substances that hold promise as a
of controlling powdery mildew (as well as pests). Anti-transpirants are emulsions and
polymers that were developed to form an impermeable film on plant surfaces to
moisture loss. Several brands are available; look for a white liquid, about the
consistancy of milk.
They are widely used on cut Christmas trees to retard drying and needle drop, and on
provide protection from drought, heat, wind and transplant shock. Since the thin film
transpiration of moisture – both in and out of the leaf – it makes sense that it would also
fungus spores from permeating the leaf surface.
Some rosarians have used antitranspirants in combination with fungicides, and feel
works better than fungicide alone. Others have used it entirely alone, and find that it
works very well
all by itself. Packaging directs us to water plants well and allow them time to take up
before spraying. Since anti-transpirants are NOT yet labeled for disease protection,
there is no
accepted formula for application. They come in various concentrations that would
require more or
less dilution – anywhere from 1 tablespoon to 1/2 cup per gallon of water. Again,
frequency is not
addressed … once a week … once a month? At this stage it’s sort of experimental. If a
residue is left
on the foliage (objectionable to you as an exhibitor) then reduce the ratio.
Whether we choose the fungicide method or the non-toxic approach to controlling
probably depends upon the degree of severity we encounter on a regular basis.
Regardless of the
product selected, it must be used on a regular basis in the proper dilution to prevent
without damaging plant tissue.
What is Blackspot?
Blackspot is a plant disease caused by a fungus (Diplocarpon rosae) that is generally
usually a source of major problems. Blackspot looks like circular black spots with
on the top side of the leaves. The tissue around the spots or the entire leaf may turn
yellow and the
infected leaf may drop off. Plants with a severe case may lose all of their leaves if not
production is often at a minimum and the quality of bloom suffers badly.
High humidity is one factor that helps the spores to germinate. The spores germinate
in 9-18 days on
a moist leaf at 70-80?F temperatures. The spores can be spread by splashing water
and by the
Rosarians themselves. The spores are wind-borne only in water drops. The spores
can be spread on
clothing, tools or even your hands, but the way it is spread most often is by infected
leaves that have
wintered over in the rose bed.
Blackspot can be satisfactorily controlled by spraying with a good fungicide every
seven to ten days
(read the label and follow the directions). There are also a number of measures that
should be taken
to keep from getting and/or controlling the disease. Avoid watering in a way that
splashes water up
on the leaves and avoid watering late in the evening with a hose or sprayer. Make
sure to clean up
the beds completely of all leaves or stems to help keep the disease from wintering
over. Always have
good ventilation through the plant and good soil drainage. Apply fungicides after a
rain to keep
down spores. Put the plants on a spray schedule and spray with a fungicide that gives
such as, Manzate?, Maneb?, Daconil? and Lime-Sulfur compounds.
There are also organic methods of controlling Blackspot. Baking soda has been tried
as a cure and
as a preventative measure. It was found that using baking soda and spray oil mixed
with water as a
spray can damage roses if it is not mixed in the proper proportions. It was also found
soda gave only moderate control of Blackspot, but appeared to be effective as a
is a new product coming on the market that has been used by our local Rose Society
that does show
promise. This product is derived from the Neem tree. It is called “Rose Defense” by
The Green Light
One other way to prevent Blackspot is to plant roses that are disease resistant. There
are some roses
that have some resistance built into their genes. But remember, they are Resistant not
still need to be sprayed on a regular schedule.
Roses should be kept on a regular spray schedule regardless of which method is
prevention is the key to controlling Blackspot.
Rose Mosaic Virus Disease
by Malcolm M. Manners, Lakeland, FL
Many of you know that the primary reason we grow roses at Florida Southern College
involvement in indexing and heat-treating roses for rose mosaic disease. While we
have had articles
about the subject in numerous other publications, over the past decade, I’ve not
subject in The Cherokee Rose, nor has there been any extensive discussion of the
subject at any of
our meetings. Yet it is a subject I believe to be quite important, particularly in that a
ignorance of the problem, could introduce a viral infection to an antique rose which
survived hundreds of years without the disease. A few simple precautions could have
infection. Also, some old rose nurseries are notorious for shipping virus-infected
plants, while others
have made a great effort to provide virus-free bushes. I certainly commend (and
The following is an updated version of a paper I presented to the Florida State
The Citrus Institute of Florida Southern College initiated a program to rid infected rose
rose mosaic (RM) disease in 1984. This paper will describe the disease, its effects on
rose plants and
their culture, and the heat therapy program at Florida Southern College.
Rose mosaic is a disease caused by a virus complex infecting cultivated roses (Rosa
hybrids). Cochran 3 reported that by 1970, most of the garden roses in the United
infected. Since then, heat therapy programs have been initiated at the Oregon State
the University of California at Davis, as well as by Bear Creek (parent company of
Perkins Roses and Armstrong Roses). The Oregon State program is now nearly
commercial rose nurseries have made use of those programs and now offer virus-free
plants for sale.
However, many nurseries have not made any attempt to provide healthy plants, and a
percentage of the roses grown and sold in Florida are infected. Florida nurseries
using Fortuniana as
a rootstock are at a particular disadvantage, since scion-source plants of new
cultivars are received
from a single source, usually on Dr. Huey rootstock, from California. If these original
infected, then all plants subsequently produced on Fortuniana rootstock will be
infected. In recent
years virtually all new cultivars, including the All America Rose Selections (AARS)
been infected with RM when received by the Florida nurserymen (personal
several nurserymen. Diagnosed by leaf symptoms.) The disease also may be spread
to other cultivars
through the use of infected rootstock. No source of indexed virus-free Fortuniana
plants has been
available until recently, although some propagators have been quite conscientious
their rootstock cuttings only from plants which have never shown symptoms of RM.
Since RM is not fatal to the plant and often has no obvious detrimental effect on a
and rosarians tend to be unconcerned about the problem. When leaf symptoms
appear on a plant, the
affected branch is pruned off, temporarily ridding the plant of its symptoms. If (as many
believe) the only effect of RM were an occasional chlorotic or disfigured leaf, there
would be little
cause for concern about the disease. However, RM has been shown to cause flower
2,3,4,8, reduced flower production 3,4,6,8,9, reduced flower size 8,9, reduced stem
caliper at the
graft union 8,9, reduced vigor 2,3,7,8,9, early autumn leaf drop 8, lower bush survival
increased susceptibility to cold injury 6, and more difficult establishment after
transplanting 8. The
symptoms are highly variable among rose cultivars and are strongly influenced by
growing conditions. Infected plants may appear to be quite healthy for much of the
year, and any
symptoms which do appear may be attributed to other causes, such as spray burn,
deficiencies, high temperature, or poor horticultural practices. It has been suggested
“deterioration” which often occurs in rose cultivars several years after their
introduction may be a
result of virus infection 1.
Rose mosaic is a complex of several viruses which cause similar symptoms in rose
plants. The most
important of these in the United States is prunus necrotic ringspot virus, a common
disease of stone
fruit trees 5. Of lesser importance in the USA are apple mosaic virus and arabis
mosaic virus. There
may be additional viruses involved in the RM complex 6. Several other virus diseases
of rose are
quite distinct from RM and will not be considered in this paper. These include rose
wilt, rose leaf
curl, rose streak, rose rosette, and rose spring dwarf.
Means of Transmission
RM is believed to be non-contagious in the field, except possibly through rare natural
There is no evidence that it ever spreads naturally in the garden or nursery, or through
or seedlings 2. Extensive tests also have failed to transfer RM mechanically (e.g., on
grafting knives, etc.) 3. The only known means for transmitting the disease is by
propagation. Cuttings rooted from infected plants, or budded plants produced from
infected scions or
rootstocks, will be infected in virtually every case. The disease is systemic, so the
entire plant is
infected, whether or not all of the branches show symptoms. A plant which is infected
at the time of
propagation will remain infected throughout its life, and a healthy plant at the time of
should remain healthy for its entire life, unless an infected scion is budded or grafted
It is probable that the disease was transferred to roses originally from one of the stone
graftage 4. It then spread from one rose cultivar to another through infected rootstocks.
practices contributed to the rapid spread of the disease in the United States:
1.Collecting scion wood for next year’s crop from this year’s budded plants in the
rather than from a separate, disease-free, scion-source garden 4. 2.Collecting
rootstock cuttings from
suckers on budded plants in the production field, rather than from a non-budded,
rootstock planting. In Europe, where rootstock plants are usually produced from seed,
quite rare 3.
Leaf symptoms of RM are highly variable, often making diagnosis difficult. Some rose
show strong symptoms, while others may be nearly symptomless. Most cultivars will
symptomless for at least part of the year. The most severe symptoms usually are seen
weather, in the spring, and are much less severe during the summer months. Some
leaves may show
“vein-banding”, in which the veins are bright orange or yellow, on a green
background. Other leaves
may show a bright yellow or white “oak leaf” or “mosaic” pattern . A very faint
chlorosis is common on the leaves of some cultivars . These symptoms often fade as
the leaf ages
and may disappear completely. The chlorotic patterns associated with RM usually do
resemble any mineral nutrient deficiency or herbicide toxicity pattern and are
reasonably reliable for
diagnosing RM. The absence of any obvious symptoms is normal, and is no
guarantee of freedom
from RM; some infected cultivars seldom show symptoms, but their performance may
The Heat Therapy Program at Florida Southern College Florida Southern College’s
program was initiated with the following goals:
1.To produce rootstock plants adapted to rose culture in Florida that are known to be
free of RM,
particularly Fortuniana and Fun Jwan Lo . 2.To rid commonly grown scion cultivars
garden rose cultivars) of RM. 3.To provide propagating material of rootstock and scion
nurseries interested in cooperating with the program, thus enabling Florida residents
disease-free plants on desirable rootstocks. 4.To maintain a RM-free garden for the
healthy germplasm of the treated cultivars. The heat therapy procedures are similar to
employed by the programs at the Oregon State University and the University of
California at Davis.
Infected scionwood is budded or grafted to Fortuniana rootstock and grown to a
2-gallon size plant.
The potted plant is placed in a controlled-environment chamber, where the
temperature is held at a
constant 38? C (100? F) for 21-35 days. The heat treatment does not cure the plant,
material can be obtained as follows: Axillary buds from the treated plant are budded
rootstocks. Most of the axillary buds on the heat-treated plant will be free of RM. Once
budlings are growing, they must be tested to insure freedom from RM, a process
We use three indexing methods:
1.Mme. Butterfly — Buds from the plant to be tested are budded to established plants
Mme Butterfly an older Hybrid Tea which shows brilliant mosaic symptoms when first
This is usually done in the autumn. The plant is allowed to grow a new flush of Mme.
leaves during the spring, and those leaves are observed for symptoms. 2.Shirofugen
– Buds from the
plant to be tested are budded to branches of Shirofugen a Japanese flowering cherry
tree. Roses and
cherries are not graft-compatible, so the graft always dies. If the bud was not infected,
branch heals over, cleanly. But if the rose bud contained mosaic virus, the virus will
to the cherry branch, which will react by producing a sticky, gummy oozing sap, and
around the graft union will die. Cherry trees don’t grow well in Central Florida, so we
the University of California to do this test for us. We ship them budwood to be tested,
3.ELISA — Enzyme-Linked Immunosorbent Assay is a laboratory method, using rabbit
It is a quick (less than one day) laboratory test, and not only tells whether any virus is
can often determine exactly which virus, and sometimes even which specific strain of
a virus, is
present. We contract with the Washington State University, to do this test, sending
them leaf samples
in cool weather.
The program at Florida Southern College is now nearly 10 years old. We have
indexed hundreds of varieties, and now maintain more than 350 virus-free scion
around 200 old garden roses. We also have virus-free rootstocks, including
Fortuniana Fun Jwan Lo
and Dr. Huey. Mosaic-free plant material is available to commercial nurseries for
it is through our cooperating nurseries that mosaic-free plants are available to the
Summary and Conclusions
Rose mosaic disease currently infects a large percentage of the roses grown in
throughout the United States. While hobbyist growers and most nurseries lack the
facilities to rid
plants of the disease, cultivars can be freed of RM by a simple heat treatment
Southern College is engaged in such a program, and offers virus-free material to
nurseries, to the extent that time and facilities will permit. Since RM is believed never
to spread by
natural means, there is no legitimate excuse for its continued existence in American
and gardens. While RM is not deadly or otherwise devastating to a rose bush,
improved growth and
more flowers of higher quality may be expected from disease-free plants, so it is to a
advantage to seek out plants known to be free of the disease.
1.You can’t cure it in your garden, but it is not going to spread from bush to bush. So
there is no
great need to dig up and destroy an infected bush. However, if you can find a
virus-free plant of the
same variety, you might want to consider replacing the bush, to gain more vigor and
production. 2.If you do your own budding or grafting, remember that those procedures
disease, so try to use virus-free scion wood and virus-free rootstocks. If you root
Fortuniana that sprouted out from the base of a grafted bush, remember that those
contain the virus if the original bush was infected. Also, any scions collected from an
will produce infected plants, when propagated. 3.Remember that a complete lack of
a healthy looking bush) is the normal situation for an infected plant. Just because a
plant appears to
be healthy, even for several years, is no guarantee that it is indeed virus-free. Only
indexing can tell
you for sure. 4.One of the major reasons so many nurseries are “cleaning up” their
stock, in recent
years, is customer demand. Please support and commend nurseries that produce
Encourage nurseries who don’t, to begin growing virus-free roses. If they know it is
you, the customer, they will likely respond favorably.
While I am not aware of any nursery which sells only virus-free plants, most of the
of the CFHRS do grow at least some clean varieties, and will gladly tell you, if you
ask, which of
their stock is clean. It will be quite a long time until all of the commercially propagated
roses can be cleaned up, but we’ve made a good start. Here’s a partial listing of older
from our program, through retail nurseries:
Insecticide chemicals have been linked to childhood immune disorders, nervous
and hyperactivity. Chemicals commonly found in insecticides-like PCB’s and DDT-
negative estrogen-like effects in some women, contributing to breast, ovary and
uterus cancer. Home
pesticide users may use an average of up to six times more pesticide per acre than
Insecticide use has increased ten-fold since 1940, but insect induced crop losses
doubled to more
than 13 percent. 25-50 percent of air sprayed pesticide does not hit the field and drifts
environment, contaminating soil, water, and air. Pesticide residues on fresh produce
can be reduced
by thorough washings with water, removing outer leaves, peeling and cooking.
However, not all
residues can be removed, especially residue from pesticides that enter fruits and
the soil. Pesticide chemicals remain in the environment long after they are no longer
used-DDT, chlordane and heptachlor can linger in the soil for more than 20 years.
organically grown foods and using alternative pesticide control methods can
chemical contamination of humans, animals and the environment.
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